1. Field of the Invention:
This invention relates to a connector for a camera and more particularly to a connector for connecting a camera body with the electric circuit of an accessory such as an interchangeable lens.
2. Description of the Related Art:
The interchangeable-lens-using cameras of the kind having bayonet mounts which are arranged to permit mounting and dismounting the interchangeable lens on and from the camera body by turning them round clockwise and counterclockwise relative to each other between their mounts have recently come to have electric circuits arranged within both the camera body and the lens to exchange between them information of varied kinds required for automatic exposure control, automatic focusing, etc. Hence, it has become popular to have many connector pins provided close to the mounts for the purpose of signal exchange.
Referring to FIGS. 8 to 11 of the accompanying drawings, a bayonet mount 1 on the side of a camera A (see FIG. 4) is disposed on the front of a camera body 4. Lock pin 2 which is provided for fixing the lens when the lens is mounted and a contact seat 3 which forms a connector on the camera side are also disposed on the front of the camera body 4. A plurality of contact pins 3a1 to 3a7 (seven in this case) are arranged to have their tips thrusted out to equal extents from the front face of the contact seat 3 by the urging forces of contact springs 3b1 to 3b7. The contact pins 3a1 to 3a7 are connected by means of a flexible printed circuit board 5 to an electric device 6 disposed on the side of the the camera body. Meanwhile, an interchangeable lens B carries a photo taking lens group 7. To the rear end face of the lens B are secured a bayonet mount 8 of the lens, a lock slot 9 which is arranged to engage the lock pin 2 of the camera body and a contact seat 10 which forms a connector on the side of the lens. The contact seat 10 is provided with a plurality (seven in this case) of contact pins 10a1 to 10a7 which are secured to the seat 10 in such a way as to have their rear ends arranged to be flush with each other. These contact pins 10a1 to 10a7 are connected to an electric device 12 of the lens via a flexible printed circuit board 11.
The bayonet mount 1 on the side of the camera body has three claws 1a1, 1a2 and 1a3 which are disposed on the inner side of the mount. The bayonet mount 8 on the side of the lens has also three claws 8a1, 8a2 and 8a3 arranged thereon to engage the above stated claws 1a1 to 1a3 respectively. The lock pin 2 on the side of the camera body engages the lock slot 9 to hold the lens in a mounted state after completion of mounting the lens on the camera.
With the interchangeable lens B mounted on the camera A, the mount faces of the bayonet mounts are in a state of overlapping each other. Then, the contact pins 3a of the camera body are pressed into contact with the contact pins 10a of the lens by the forces of the contact springs 3b at an adequate degree of contact pressure The contact pins 3a1 to 3a7 are thus electrically connected to the contact pins 10a1 to 10a7. This enables the electric device 6 on the side of the camera body and the electric device 12 on the side of the lens to exchange electrical signals.
The electrical connection which results from the mounting action on the interchangeable lens B is attained in a manner as shown in FIG. 8. The contact seat 10 on the side of the lens B moves in the direction of arrow C as the lens B is turned for mounting. Then, the contact pins on the side of the camera body are pushed by a slanting edge face 10b of the contact seat 10 of contact pins on the side of the order of pins 3a7 to 3a1 thus sliding alternately over the surface of the contact seat 10 of the lens and over the contact pins 10a1 to 10a7 of the lens while the contact springs are compressed one after another in the order of springs 3b7 to 3b1. These contact pins 3a1 to 3a7 of the camera are thus eventually brought into pressed contact with the contact pins 10a1 to 10a7 respectively on one and the same plane as shown in FIG. 9 when the lens is completely mounted on the camera body.
With the conventional connector arranged as shown in FIGS. 8 and 9, the contact pin 10a1 of the lens B first comes into sliding contact with the contact pin 3a7 of the camera body when the lens B is turned on the camera body. The mounting operation comes to an end when the contact pin 10a1 of the lens has come into sliding contact with the contact pins 3a6 to 3a1 after its contact with the pin 3a7. Following the contact pin 10a1 during the mounting process, other contact pins of the lens also come into sliding contact with the contact pins of the camera body one after another. More specifically, the pin 10a2 comes into contact with the pins 3a7 to 3a3,--, the pin 10a6 with the pins 3a7 and 3a6 and the pin 10a7 with only the pin 3a7.
The contact pins 10a1 to 10a7 are fixed and have their surfaces arranged either to be flush with the connecting surface of the contact seat 10 of the lens or to be recessed. Therefore, they tend to have dust or some foreign matter stick to them. The foreign matter sticking to the contact pins 10a1 to 10a7 of the lens is removed and the surfaces of the pins are cleaned by the sliding contact which takes place with the contact pins 3a7 to 3a1 of the camera body in mounting the lens on the camera body. In this instance, while the surfaces of the contact pins 10a1 to 10a6 can be cleaned with the contact pins 3a7 to 3a1 sliding from one end (left- or right-hand side end as viewed on FIGS. 8 and 9) over to the other end at least once, the contact pin 10a7 cannot be completely cleaned, because the corresponding contact pin 3a7 disposed on the side of the camera body slides only to a middle part from the right-hand side end of the pin 10a7 (as viewed on FIGS. 8 and 9). Therefore, a foreign matter sticking to the contact pin 10a7 tends to remain unremoved. Besides, every time the interchangeable lens B is mounted on the camera A, the foreign matter sticking to the contact pins 10a1 to 10a6 of the lens is carried toward the last contact pin 10a7 by the contact pins 3a7 to 3a2 of the camera body to be accumulated on the contact pin 10a7 of the lens. The accumulated foreign matter then tends to cause inadequate contact. Normal operations of the camera and the lens are hardly assured under such a condition.